User:Sarah Labianca/Notebook/Smyth Lab/2012/03/01

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Choosing an accelerometer

I have decided to use the ADXL345 triple axis accelerometer. The reasons for this choice are as follows:

-The measurement range is variable, we can choose ranges of ±2g, ±4g, ±8g and ±16g. This means that we aren't obligated to a certain measurement range, and can adjust this based on our needs. -The importance of the variable measurement ranges lies in the effect it has on resolution. The larger the g range, the smaller the resolution of our measurements. This is because the 1024 possible data points for measurements are divided up evenly over the g ranges. If we discover that the pendulum falls withing the ±4g range, we can use ±4g instead of ±8g or ±16g, effectively giving us a larger resolution, as compared to an accelerometer without variable ranges where we would be stuck using a certain, nonadjustable measurement range. This is even more useful because we do not know the force range of the pendulum.

- To measure impacts, bandwidth (the amount of data that can reliably be output per second) needs to be in the hundreds of Hz. The ADXL345 has a variable hertz range of 6.25 Hz to 3200 Hz, allowing us to read impacts.

-The ADXL345 should interface well with an Arduino, and comes mounted on a breakout board.


ADXL345 Data Sheet


Side notes

Today I found a piece of software called Fritzing that allows one to flesh out PCB board and breadboard designs virtually. A video of someone using Fritzing:



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